My problem is exactly as you described, I am trying to resolve now. My Samsung Model # is LN-S4695D X/XAA. I don't beliece it's the display either. Menu "dialogue" boxes display just fine "over" these horizontal "lines" that are pixelated and maybe 10 pixels high. I have ~no~ vertical lines/errors/problems. I just replaced my T-Con board to no avail.
My 46'' Samsung LCD HDTV has white lines going across the screen when watching cable, DVD, blue ray, etc. The weird thing is that the lines are not at a constant place, and don't show up when the TV has no component on (blue screen) or when the menu is up (the lines remain, but not on the area of the screen where the menu options are located. They remain only in the background as if behind the menu). These lines also flicker with color once in a while, and change location depending on the component being used. This leads me to believe it is not a panel problem since all the pixels seem to work when nothing is on. I've called Samsung to see if they could help, but since the TV is about 3 years old, the warranty is out and we simply can't see ourselves paying 300 bucks to have someone just look at it before ever finding out the problem. As a matter of fact this TV was my step-father's so he just bought a newer/bigger LED one instead of forking over the cash. I just don't personally see a reason to get rid of the damn thing when I can easily upgrade my 32'' to the 46'' if I can get this fixed. Any advice/help on how I can get this fixed in a cheaper manner is GREATLY appreciated!